I just found this in the wiki under bugs:
- "A merchant that has been killed by a plasma weapon turns into a goo pile that can be used to initiate a conversation once the merchant has respawned. The merchant can be quite a distance away but the conversation zooms in and initiates anyways."
This would suggest they do but I can't say for sure.
Heh. That could be used to "anchor" the merchant on a convenient spot instead of having to chase him down!
That description does suggest that they respawn. I wonder if their mercenaries do though. In the beginning of the game you usually see merchants accompanied by mercs, but later on they wander around unaccompanied.
P.S. I decided to help the merchants after all. Killed the Legion boys and the assassins who came after me right away. The caravan apparently felt obliged to repay the favor, so they walked up the hill and helped me clear out the nasty pack of Nightstalkers at the entrance to the Walking Box Cavern. I really don't think I could have taken them out on my own. One merc died.